Another little LINQ error you might encounter from time to time. Ran into this yesterday while building out some queries, and figured it was worth a quick post. Starting with a basic stream, I needed to group by a set of fields in the stream and calculate some basic aggregates.

See the subtle yet annoyingly obvious after the fact mistake I made? I grouped by sensorGroups, but windowed over inputStream. Fix this to use the same stream for the window and the group resolves the error.